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Electrophysiology
Published in A. Bakiya, K. Kamalanand, R. L. J. De Britto, Mechano-Electric Correlations in the Human Physiological System, 2021
A. Bakiya, K. Kamalanand, R. L. J. De Britto
The cardiopulmonary system consists of blood vessels that carry nutrients and oxygen to the tissues and removes carbon dioxide from the tissues in the human body (Humphrey & McCulloch, 2003; Alberts et al., 1994). Blood is transported from the heart through the arteries and the veins transport blood back to the heart. The heart consists of two chambers on the top (right ventricle and left ventricle) and two chambers on the bottom (right atrium and left atrium). The atrioventricular valves separates the atria from the ventricles. Tricuspid valve separates the right atrium from the right ventricle, mitral valve separates the left atrium from the left ventricle, pulmonary valve situates between right ventricle and pulmonary artery, which carries blood to the lung and aortic valve situated between the left ventricle and the aorta which carries blood to the body (Bronzino, 2000). Figure 3.9 shows the schematic diagram of heart circulation and there are two components of blood circulation in the system, namely, pulmonary and systemic circulation (Humphrey, 2002; Opie, 1998; Milnor, 1990). In pulmonary circulation, pulmonary artery transports blood from heart to the lungs. The blood picks up oxygen and releases carbon dioxide at the lungs. The blood returns to the heart through the pulmonary vein. In the systemic circulation, aorta carries oxygenated blood from the heart to the other parts of the body through capillaries. The vena cava transports deoxygenated blood from other parts of the body to the heart.
The patient with acute cardiovascular problems
Published in Peate Ian, Dutton Helen, Acute Nursing Care, 2020
The cardiovascular system is responsible for the circulation of blood to and from the organs and tissues of the body. Blood must be transported under a sufficient pressure to facilitate adequate movement of oxygen, nutrients, hormones, electrolytes, water and other blood products to their target locations. In addition to being a transportation system to the tissues of the body, the cardiovascular system facilitates the removal of waste products from cellular activity.
Basic medicine: physiology
Published in Roy Palmer, Diana Wetherill, Medicine for Lawyers, 2020
The heart is the muscular pump that drives blood around the body. It has long been known that blood will spurt from a cut artery under high pressure, but it was thought to oscillate to and fro until William Harvey showed that blood circulates from small arterial branches through tiny vessels in the tissues (capillaries) before being collected by veins and returned to the heart The dynamo behind this circulation is the heart, which contracts 60–80 times per minute throughout an individual’s life. The heart contains four chambers and is responsible for two separate circulatory systems (Figure 1.1). The systemic circulation supplies all the organs in the body with oxygenated blood, while the pulmonary circulation delivers exhausted blood to the lungs where it is replenished with oxygen. The heart chambers comprise two atria which collect the blood and pass it through valves into the two ventricles, which contract forcefully to distribute blood throughout the body. The cardiac cycle consists of diastole, the phase of filling, and systole in which contraction of the atria is immediately followed by contraction of the ventricles.
The role of a point-of-care ultrasound protocol in facilitating clinical decisions for snakebite envenomation in Taiwan: a pilot study
Published in Clinical Toxicology, 2021
Cheng-Hsuan Ho, Ahmad Khaldun Ismail, Shing-Hwa Liu, Yuan-Sheng Tzeng, Ling-Yuan Li, Feng-Cheng Pai, Chia-Wei Hong, Yan-Chiao Mao, Liao-Chun Chiang, Chin-Sheng Lin, Shih-Hung Tsai
Several studies have highlighted the benefit of sonography in identifying the location and extension of edema after snakebite [23–25]. Wood et al. used sonography to identify damaged tissue in the intramuscular layer in patients who developed ACS following snakebite [23]. When ACS is established, a high IP leads to compromised blood circulation in distal vessels that results in nerve injury. Normal arterial blood circulation is pulsatile and influenced by vessel resistance, endothelial function, blood pressure, vascular compliance and resistance [26]. Using Doppler ultrasound, the systolic and diastolic pressures can be compared in the same pulsatile wave [26]. Increased diastolic retrograde arterial flow (DRAF) can be observed in the affected artery in the same compartment where there is a restriction of the compartment space, e.g., increased IP [27]. In a pilot study of healthy volunteers, DRAF was assessed serially at different cuff pressures. Greater percentages of DRAF were detected as the cuff pressure was increased from 40 mm of Hg, equal to the diastolic blood pressure, and equal to the mean arterial pressure [27]. Point-of-care ultrasound (POCUS) provides an ideal tool for the serial evaluation of the location of edema and the presence of DRAF in the affected limb. The noninvasive nature of POCUS theoretically minimizes bleeding complications following invasive catheter insertion in patients with coagulopathy following Viperidae bite envenomation [28].
Right Ventricular-Pulmonary Arterial Coupling and Outcomes in Heart Failure and Valvular Heart Disease
Published in Structural Heart, 2021
Bahira Shahim, Rebecca T. Hahn
Compared with the systemic circulation, pulmonary circulation has a much lower vascular resistance, greater pulmonary artery distensibility, and a lower peripheral pulse wave reflection coefficient.12 Pulmonary vascular impedance reflects the opposition to pulsatile flow, and determines, together with pulmonary vascular resistance (PVR), the RV afterload.9 RV afterload is reflected by arterial elastance (Ea), a load-independent measure of “total” ventricular afterload (both pulsatile and resistive components). It is measured as RV end-systolic pressure divided by stroke volume.24 PVR is a measure of the resistance of both capillaries and veins and is calculated as the difference between the mean pulmonary arterial pressure and pulmonary capillary wedge pressure, divided by the cardiac output. In the normal RV, mean pulmonary artery pressure is a reasonable approximation of end-systolic pressure. Thus, in the normal RV Ea could be estimated as PVR x heart rate.25 Although PVR represents only the resistive component of Ea, and pulmonary arterial compliance represents the pulsatile component, the latter contributes only ~23% to total afterload26 in normal patients and those with arterial pulmonary hypertension (PH) and support the use of the simplified formula. However, if post-capillary PH is present, the pulsatile component of Ea increases27 and stroke work is significantly reduced.28 Taking into account both resistive and pulsatile components of Ea may then be more important.
Sepsis-associated encephalopathy and septic encephalitis: an update
Published in Expert Review of Anti-infective Therapy, 2021
Simone C. Tauber, Marija Djukic, Johannes Gossner, Helmut Eiffert, Wolfgang Brück, Roland Nau
The pathophysiology of SAE still is incompletely understood. The immune privilege of the CNS depends on the morphological architecture of its borders resembling a medieval castle. The blood-brain barrier (BBB) and blood-CSF barrier serve as the outer walls of the castle [45]. The brain senses a septic infection under physiological conditions by several ways: (a) leaky regions of the BBB barrier in the circumventricular organs (CVOs) comprising approximately 1:5000 of the entire capillary surface area, (b) afferent fibers of several nerves, particularly of the vagus nerve, and c) direct communication across the BBB [46]. The brain has an important role in the regulation of the immune system, particularly via the neuroendocrine network. The main abnormalities in sepsis comprise (a) dysfunction of the neuroendocrine network, (b) diffuse neuroinflammation with BBB leakage and inflammation-induced damage to neurons and glial cells, (c) impaired circulation leading to impaired autoregulation and ischemia, and (d) imbalance of neurotransmitters leading to excitotoxicity [11,14] (Figure 1). These four major pathophysiologic mechanisms are discussed in detail below.